# How do you calculate the formal charge of O3?

Typically, a Lewis structure of O=stackrel(ddot)O^(+)-O^(-), would be depicted. Going from left $O$ to right $O$ and including the 2 inner core electrons on each atom, there are 8, 7, and 9 electrons around each oxygen centre, resulting in formal charges of $0$, $+ 1$, and $- 1$, respectively. Of course, I can draw the other resonance structure, but the Lewis structure has the same electronic formulation. The $\angle O - O - O$ $\cong {117}^{\circ}$; this is slightly LESS than the normal $s {p}_{2}$ bond angle of ${120}^{\circ}$, due to disproportionate influence of the oxygen lone pair, which tends to compress $\angle O - O - O$.